1. Field of the Invention
This invention relates to a damper which is used for a torsional vibration damper which couples an engine flywheel with a transmission input shaft or for a damper disc for an automobile clutch, and especially to a liquid viscous damper which develops a hysteresis torque by means of a viscosity of liquid.
2. Description of the Related Art
A damper of such type is generally equipped with a output-side driven plate and an input-side drive plate which houses the foregoing driven plate by covering both sides and outer peripheral side of the driven plate, and has a damper mechanism for developing a torsional torque between the both plates.
Divided liquid chambers 38 & 39 are formed in a drive plate 3 as shown in FIG. 5, liquid is filled in these chambers and a choke S1 is provided between the divided liquid chambers 38 & 39. The choke S1 is formed between a notch 60 formed on a driven plate 23 and an inward facing projection 62 formed on the drive plate 3.
In order to let a hysteresis torque change in two stages for example, a stepped part 61 is formed on a midway of the notch 60 so that, when the drive plate 3 is twisted relatively to the driven plate 23 from a state of FIG. 5 for example to a rotation direction R side by .theta. 1 or to an opposite to the rotation direction R side by .theta. 2, a clearance of the choke S1 is changed from d1 to d2 and the hysteresis torque is increased from H1 to H2 as shown by FIG. 6. However, in the event a structure which changes the hysteresis torque by only the torsion angle of the drive plate 3 relative to the driven plate 23 is employed, it becomes impossible to develop the small hysteresis torque H2 in response to circumstances in a large torsion angle range and further it becomes impossible to develop the large hysteresis torque in response to circumstances in a small torsion angle range.